<!DOCTYPE html>
<html lang="en">

<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
  <style>
    .red {
      background: red;
      border: 1px solid black;
    }
  </style>
</head>

<body>
  <div id="test">
    <div class="child">1</div>
    <div class="child">2</div>
    <div class="child">3</div>
  </div>
  <script src="dom2_test.js"></script>
</body>

</html>